1. Field of the Invention
The present invention relates to an circuit board and, more particularly, to an circuit board that allows an integrated circuit package to be precisely and easily mounted.
2. Background Art
Recently, as the semiconductor technologies have developed, integrated circuits having complex functions have been introduced. As an example of such integration, the integration of a central processing unit (CPU) which performs very important functions of the microcomputer has progressed rapidly. In addition, to emit heat from the integrated circuit having complex functions, the shape of the package of the integrated circuit has been changed. For example, the CPU of a microcomputer has been developed from an 8086 8-bit processor to 80386, 80486, and 80586 32-bit processors through 80-286 16-bit processors. As CPUs having higher efficiencies have been developed, the number of the leads of the CPU rapidly increases. Moreover, as the density of the leads increases, new technologies for mounting the CPU on the printed circuit board have been developed.
In recent days, with high efficiency being required even in a small computer such as a notebook computer, a Pentium.TM. processor which functions as the CPU is mounted and will continue to be mounted in compliance with the requests of users. However, in the case of notebook computers, which require circuits that are further miniaturized, the use of small integrated circuits has become necessary. As the external size of integrated circuits becomes smaller, the shape of the package becomes more significant due to the heat that is generated. An integrated circuit of the TCP type is a very small compartment that includes 320 pins and has a spacing of 0.2 mm between the leads. As a result of the size of the integrated circuit package and the even smaller size of the printed circuit board, the exact mounting of integrated circuit devices has been an area of continuing research. Some techniques for mounting integrated circuit packages are shown, by way of example, in U.S. Pat. No. 4,663,695 to Ohkawara entitled Holding Device for Mounting an Electronic Component on a Printed Circuit Board, U.S. Pat. No. 5,045,976 to Guilleminot entitled Device for Mounting a Metal Element on a Board, U.S. Pat. No. 5,160,270 to Reymond entitled Integrated Circuit Packages Using Tapered Spring Contact Leads for Direct Mounting to Circuit Boards, U.S. Pat. No. 4,054,901 to Edwards entitled Index Mounting Unitary Heat Sink Apparatus with Apertured Base, U.S. Pat. No. 5,684,675 to Taniguchi entitled Semiconductor Device Unit Having Holder, U.S. Pat. No. 5,277,612 to Windham entitled Carrier for Guiding and Supporting Semiconductor Devices, U.S. Pat. No. 5,555,488 to McLellan entitled Integrated Circuit Device Having Improved Post for Surface-Mount Package, U.S. Pat. No. 5,557,504 to Siegel entitled Surface Mountable Integrated Circuit Package With Detachable Module, U.S. Pat. No. 5,671,125 to Russell entitled Vertical Package Mounted on Both Sides of a Printed Circuit Board, U.S. Pat. No. 5,155,905 to Miller, Jr. entitled Method and Apparatus for Attaching a Circuit Component to a Printed Circuit Board, U.S. Pat. No. 5,680,057 to Johnson entitled Integrated Circuit Testing Assembly and Method, U.S. Pat. No. 5,680,057 to Johnson entitled Integrated Circuit Testing Assembly and Method, and U.S. Pat. No. 4,969,827 to Hahs, Jr. entitled Modular Interconnecting Electronic Circuit Blocks.
Often integrated circuit packages are mounted on a ball grid array (BGA) that has lead pins located on the bottom' surface of the BGA. The integrated circuit package is then placed on a printed circuit board by a surface mount technology (SMT) handler. When the BGA package is held and moved by the programmed SMT handler to be mounted on a printed circuit board, the lead pins of the integrated circuit supporting BGA package must be exactly positioned on the printed circuit board. Failure of the lead pins to be exactly positioned on the pads leads to the poor mounting of integrated circuit packages.
I have noticed, however, that since the lead pins of the BGA package are too short, it is difficult to determine whether the BGA package is correctly mounted on the printed circuit board. As the SMT handler moves during the package mounting operation, any deviation from the proper position of the SMT handler leads to the incorrect positioning of the integrated circuit package on the printed circuit board. I have further noticed that it is often difficult to determine whether the integrated circuit package is correctly mounted on the printed circuit board. I expect that an circuit board that made it easier to precisely position an integrated package would improve the efficiency of production